install Windows 10 on micro SD

I have two Atomic Pi boards, one of them has been installed windows 10 successfully on the on-board EMMC, which is only 14GB. The other one, I'm trying to install a Windows 10 on the micro SD card. I have formatted the micro SD as NTFS. I have the windows install USB flash drive ready and can boot from it. but when I go thru the settings, there is no micro SD storage shows up in the installation destination drive list. Can anyone give me some suggestions? Thanks!

I used Rufus to install Windows 10 (Image selection Windows To Go) on a micro SD card.
I could then boot off of the SD card. That being said, I think that it is just too slow, much slower than the eMMC.
Windows 1903 will require an additional 7GB of disk space, so installing new version of Windows 10 will require a micro SD card or USB stick install.